CrawlSpider

（1）继承自scrapy.Spider

（2）独门秘籍

　　CrawlSpider可以定义规则，再解析html内容的时候，可以根据连接规则提取出指定的链接，然后再向这些链接发送请求。

　　所以，如果有需要跟进链接的需求，意思就是爬取了网页之后，需要提取链接再次爬取，使用CrawlSpider是非常合适的。

1.创建项目

本案以爬取读书网符合规则的说有页码内数据。

（1）创建项目 scrapy startproject 项目的名字

（2）跳转到spiders文件夹的目录下

（3）创建爬虫文件

　　scrapy genspider -t crawl 爬虫文件的名字 爬取的域名

 

 

 2.核心代码

read.py核心代码

import scrapy
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from scrapy_readbook.items import ScrapyReadbookItem


class ReadSpider(CrawlSpider):
    name = 'read'
    allowed_domains = ['www.dushu.com']
    # https://www.dushu.com/book/1188.html的时候，爬取的数据少一页
    # 这是因为起始页的地址不符合校验规则，用CrawlSpider爬取一定出现这个问题。根据观察要改成以下形式
    start_urls = ['https://www.dushu.com/book/1188_1.html']

    rules = (
        # allow为正则表达式,\d代表数字，+代表多个
        Rule(LinkExtractor(allow=r'/book/1188_\d+\.html'), callback='parse_item', follow=False),
    )

    def parse_item(self, response):
        img_list=response.xpath('//div[@class="bookslist"]//img')
        for img in img_list:
            name = img.xpath('./@alt').extract_first()
            src = img.xpath('./@data-original').extract_first()
            book = ScrapyReadbookItem(name = name,src=src)
            yield book

items.py数据结构

# Define here the models for your scraped items
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/items.html

import scrapy

# 定义数据结构
class ScrapyReadbookItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    # 名称
    name = scrapy.Field()
    # 路径
    src = scrapy.Field()

pipelines.py管道

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://docs.scrapy.org/en/latest/topics/item-pipeline.html


# useful for handling different item types with a single interface
from itemadapter import ItemAdapter

# 管道
class ScrapyReadbookPipeline:
    # 爬虫文件运行前执行这个方法
    def open_spider(self,spider):
        self.fp = open('book.json','w',encoding='utf-8')

    def process_item(self, item, spider):
        self.fp.write(str(item))
        return item

    # 爬虫运行后执行这个方法
    def close_spider(self,spider):
        self.fp.close()

settings.py配置

# Scrapy settings for scrapy_readbook project
#
# For simplicity, this file contains only settings considered important or
# commonly used. You can find more settings consulting the documentation:
#
#     https://docs.scrapy.org/en/latest/topics/settings.html
#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'scrapy_readbook'

SPIDER_MODULES = ['scrapy_readbook.spiders']
NEWSPIDER_MODULE = 'scrapy_readbook.spiders'


# Crawl responsibly by identifying yourself (and your website) on the user-agent
#USER_AGENT = 'scrapy_readbook (+http://www.yourdomain.com)'

# Obey robots.txt rules
ROBOTSTXT_OBEY = True

# Configure maximum concurrent requests performed by Scrapy (default: 16)
#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)
# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay
# See also autothrottle settings and docs
#DOWNLOAD_DELAY = 3
# The download delay setting will honor only one of:
#CONCURRENT_REQUESTS_PER_DOMAIN = 16
#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)
#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)
#TELNETCONSOLE_ENABLED = False

# Override the default request headers:
#DEFAULT_REQUEST_HEADERS = {
#   'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
#   'Accept-Language': 'en',
#}

# Enable or disable spider middlewares
# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html
#SPIDER_MIDDLEWARES = {
#    'scrapy_readbook.middlewares.ScrapyReadbookSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'scrapy_readbook.middlewares.ScrapyReadbookDownloaderMiddleware': 543,
#}

# Enable or disable extensions
# See https://docs.scrapy.org/en/latest/topics/extensions.html
#EXTENSIONS = {
#    'scrapy.extensions.telnet.TelnetConsole': None,
#}

# Configure item pipelines
# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html
ITEM_PIPELINES = {
   'scrapy_readbook.pipelines.ScrapyReadbookPipeline': 300,
}

# Enable and configure the AutoThrottle extension (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/autothrottle.html
#AUTOTHROTTLE_ENABLED = True
# The initial download delay
#AUTOTHROTTLE_START_DELAY = 5
# The maximum download delay to be set in case of high latencies
#AUTOTHROTTLE_MAX_DELAY = 60
# The average number of requests Scrapy should be sending in parallel to
# each remote server
#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0
# Enable showing throttling stats for every response received:
#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings
#HTTPCACHE_ENABLED = True
#HTTPCACHE_EXPIRATION_SECS = 0
#HTTPCACHE_DIR = 'httpcache'
#HTTPCACHE_IGNORE_HTTP_CODES = []
#HTTPCACHE_STORAGE = 'scrapy.extensions.httpcache.FilesystemCacheStorage'

运行结果：

代码地址：https://gitee.com/heating-cloud/python_spider.git

标签：en,CrawlSpider,爬虫,item,scrapy,html,https,docs
来源： https://www.cnblogs.com/ckfuture/p/16330109.html